Vaccines and antibiotics are currently the only two proven means for protecting aquatic animals of the classes Osteichtyes and Crustacea from disease in aquacultural settings. However, several of the pathogenic diseases caused by bacterial, vital, fungal and protozoan diseases, cannot be effectively prevented by vaccination nor treated with antibiotics. Several workers in the field have tried to develop alternative prophylatic treatments for aquatic animals in the classifications Osteichthyes and Crustacea in aquacultural settings, particularly the use of immunostimulatory compounds.
Although little is known about the immune system of fish and crustaceans, some compounds do appear to enhance the microbe killing activity of macrophages in fish. It has been reported that killed mycobacteria and muramyl peptides have enhanced the resistance of rainbow trout (Salmo gairdneri Richardson) against several pathogens. Additionally, it appears that extracts from a marine tunicate will increase the resistance of American eels (Anguilla rostrata LeSeur) against infection by Aeromonas hydraphila. However, none of these compounds have been demonstrated to be a suitable means for protecting fish or crustaceans from diseases in aquacultural settings.
Immunostimulatory compounds have also been identified which are effective for mammalian systems such as glucan. Glucan generically refers to a variety of polysaccharides containing glucose as the only glycosyl unit. Previous studies have demonstrated that specific beta-1,3 glucans are potent activators of macrophage/monocyte cell series and complement as well as lymphocytes of experimental warm-blooded animals. Some evidence has even suggested that glucan may activate arthropod and plant host defense mechanisms. Additionally no studies have yet been published which establish that yeast glucans actually function as immunostimulator in aquatic animals in the classifications Osteichthyes (such as salmon and trout) and Crustacea (such as lobsters and shrimp) in aquacultural settings.
Therefore, it would be a significant contribution to the aquacultural industry to provide a means of enhancing the resistance of aquatic animals In of the classifications Osteichthyes and Crustacea to disease.
It is thus an object of the present invention to provide a glucan preparation from yeast which enhances the resistance of aquatic animals in the classifications Osteichthyes and Crustacea to diseases in aquacultural settings.
Additionally, it is an object of the present invention to provide a process for the production of a glucan preparation suitable for administration to aquatic animals in the classifications Osteichthyes and Crustacea in aquacultural settings.
Further it is an object of the present invention to provide a process for enhancing the resistance of aquatic animals in the classifications Osteichthyes and Crustacea in aquacultural settings to diseases by administering an effective amount of a glucan preparation.
It is also an object of the present invention to provide a process for enhancing the effect of vaccines for aquatic animals in the classifications Osteichthyes and Crustacea in aquacultural settings by administering an effective amount of a glucan preparation together with the vaccine antigen(s).